Fire alarm system



Jan. 19, 1960 p. BREDEsEN 2,922,147

FIRE ALARM SYSTEM Filed Feb. 17. 1954 ADM 1 IN V EN TOR.

Hwg/P A! Erma-sew 25% lrraA? United States Patent FIRE ALARM SYSTEM Philip N. Bredesen, Cleveland, Ohio Application February 17, 1954, Serial No. 410,807 Claims. or. 340-227 The present invention relates to a fire alarm system, and more particularly, to a system for detecting and indicating the existence of a condition indicative of a fire.

An important object of the present invention is to provide a novel and improved condition control or alarm system, particularly a fire detecting and indicating system, having one or more condition sensing stations and which does not involve the making or breaking of contacts at the station, the system being inexpensive to install and maintain requiring only single lines into and out of each station and being capable of distinguishing between a fault in the system and the presence of the condition to be controlled or indicated.

Another object is to provide a novel and improved closed circuit fire detecting system of the type indicated above which is responsive to a change of electrical impedance in the system occasioned by the existence of a fire condition to indicate the presence of the condition and which includes fault indicating means responsive to an interruption of current in the system.

Another object of the present invention is to provide a fire detecting or condition control system of the type indicated above which utilizes simple, trouble-free variable impedances, preferably variable inductances, which are reliable in operation and require little maintenance.

A further object of the present invention is to provide a fire detecting or condition control system of the type referred to above in which an alternating current and a direct current are established in series connected condi tion detecting stations comprising variable impedance devices preferably inductances, having two finite impedance values and means to change the magnitude of the impedance upon the occurrence of the condition to be controlled which may be indicative of a fire, the system including means responsive to a variation in current due to the change of impedance to indicate the existence of the condition and means responsive to an interruption of the direct current to indicate the existence of a fault in the system.

An additional object of the present invention is to provide a fire detecting device comprising an inductance device having a movable core, the core having a first position wherein the inductance of the device is at a minimum and a second position wherein the inductance of the device is substantially greater than the minimum value, the core being biased to one of the positions, and means responsive to a fire condition to hold the core in its other position and release the core for movement to its biased position upon the occurrence of the fire condition.

Other objects and advantages of the invention will be apparent from the following detailed description of the preferred form of the invention, reference being made to the accompanying drawings forming a part hereof and wherein Fig. 1 is a schematic circuit diagram of a fire detecting system embodying the present invention;

Patented Jan. 19, 1960 Fig. 2 is a plan view of a fire detecting element suitable for use with the present invention; and Fig. 3 is a sectional view taken approximately along line 3-3.of Fig. 2.

Fig. 4 is a fragmentary view of a detecting station responsive to a pressure condition.

Fig. 5 is a schematic view of a modified power supply suitable for use in the present invention.

The present invention contemplates the provision of a fire detecting or condition control system having one or more condition or fire detecting stations each comprising a variable impedance, preferably a variable inductance, having two finite values and means to change the magnitude of the impedance from one value to the other upon the occurrence of a fire or condition to be controlled. An alarm or other control or indicating means responsive to the change in impedance value is connected in series with the detecting stations to provide an indication of the existence of a fire or other condition and fault indicating means responsive to an interruption of current in the system is provided to indicate the existence of a fault. Preferably an alternating current and a direct current are established in the impedance devices with the indicating or control means being responsive to a change in the alternating current due to a change in the reactance or impedance at the detecting station where the condition occurs and the fault indicating means being responsive to an interruption of the direct current in the system.

While the present invention is suitable for use in controlling or indicating other conditions, it is particularly useful as a fire or fire condition detecting system. Referring to the drawings, Fig. 1 shows schematically a plurality of fire detecting stations 10 connected in series. A power supply 11 is provided for establishing an alternating current and a direct current in the series connected fire detecting stations 10. The term alternating current as used in the present application refers to any varying current which will appear as an alternating current to a reactance such as an inductance and includes varying unidirection current. The fire detecting stations 10 are also connected in series with parallel connected relays 12, 13, the relay 12 being a DC. relay and controlling the operation of the fault indicator and the relay 13 being an AC. relay and controlling the operation of the fire alarm. One side of each of the coils of relays 12 and 13 is connected to ground.

The power supply 11 may suitably comprise a transformer 14 having its primary connected to a suitable AC. power supply and having two secondary coils 15, 16. The secondary coil 16 has one side connected to a terminal 18 of a four terminal rectifier bridge 19 having terminals 18, 20, 21, 22, the other side of coil 16 being connected to terminal 20 opposite the terminal 18. The terminal 21 of the bridge intermediate, terminals 18, 20 is connected to one side of the series connected fire de tecting stations 10 while .the remaining terminal 22 of the bridge is connected to one side of the secondary coil 15 of the transformer 14. The other side of secondary coil 15 is grounded. Each leg of the bridge 19 contains a circuit element 23 which conducts in one direction only. The elements 23 conduct in the direction illustrated in the circuit diagram so that the alternating current induced in the secondary coil 16 is fully rectified before being impressed upon the fire detecting stations 10 while the wave shape of the alternating current induced in the secondary coil 15 is half wave rectified and impressed on the stations. The rectified output of the coils 15, 16 impressed on the stations 10 will be pulsating and may be considered as a current having a DC. component and an AC. component, as will be well understood by those skilled in the art. It is these components which are used in the detecting system to actuate various relays upon the occurrence of certain conditions. If desired, the

power supply of Fig. 1 maybe replaced by any conventional source of current having; A.C; and D .C. ;components such as the power-supply shown in Fig. comprising a transformer T having-its -seconjdary connected in series with a battery B and terminals 24, 24a, the latter terminal being grounded and the former beingconnected to stations in the manner of terminal 210f the bridge19.

The fire detecting stations 10-preferably comprise an inductance with a movable core which is held in a position where the inductance has a minimum value under normal conditions and is caused to move to a position where theinductance-at the fire detecting station is-substantially greater than the minimumvalue upon the occurrence'of a fire condition. The relays '12 and 13 are I energized in the'absence of a fire andthe currents flowing in the system are related so that the relay-13 will drop out when a change of impedance occurs at one of the stations while the relay 12 is held in until the DC. current component in the system is'interrupted. When the system illustrated in Fig. l isin its normal condition the relays 12 and 13 are energized and the normally closed contacts 25 of the relay 13' are open while the normally open contacts 27 of relay 12are closed and its normally closed contacts 28 are opened. Inthis condition the electrical circuit to the fire alarm, including wire 30 from a suitable power supply, normally open contacts 27 of relay 12, normally closed contacts 25 of relay 12, and wire 31 to the fire alarm or indicator 32, is'open at the contacts 25 since the relay 13 is primarily energized by the alternating current. I fl If'afire occurs at any one of the fire detecting stations 10 the inductance change at thestationoccasioned by the fire causes a substantial reduction in the alternating When conditions are normal and'th'ere is no fire the contacts 28 are open and the faultindicating 7 means deenergized. The faultindicating means is not energized upon the occurrence of a fire since the relay 12 remains energized; If, however, an open-occurs in the system both relays 12 and 13 will drop-- out causing both the contacts 28 to close thereby energizing the fault indicating means. The fire alarm is notenergized in the event an open circuit condition occurs since the contacts 27 in the fire alarm circuit are open when the relay 12 is dropped out breaking the circuit to the'fire alarm. Relay 12 will also drop out to indicate fault when'a short to ground occurs in the system since one sided coil 15 is grounded.

Figs. 2 and 3 illustrate a suitable element forum as a fire detecting station, the element comprising a-cupshaped housing 37 "having an inductance coil 38'located adjacent the bottom 40 of the housing and adapted to receive a movable core' 39. The cup-shaped housing 37 is provided with a peripheral flange 41 at its'op'en end adapted to be used in supporting the element froma ceiling or other supportrneans. The housing'is closed by a circular member 42-having'diametrical opposed openings 43, 44 therein. V

An annular-insulator 45 is mounted on the underside of the member 42 and is adapted *to, receive machine screws 46, 47 located in theop'enings 43, 44 respectively. The machine screws 46,47 are adapted to. serve as terminals for the element and have connected thereto'the'lead wires to the inductance coil 38. The-movable core :39 is supported vertically withi-n the housing 37 and is adapted to be moved into and out of the inductance coil 38. The core39 is held in a position substantially out of the coil 38 by fusible material 51 located on an annular plate 52 supported transversely of a tubular portion 53 extending from the bottom 40 of the cup-shaped housing 37 and communicating with the inside of the housing. The axis of the tubular member coincides with the axis of the housing 37 and the coil 38. A rod 54 of material having low magnetic permeability extending axially from the core 39 passes through the opening in the annular plate 52 andspaces the core 39 therefrom. Therfusible material 51 forms a soldertype connection between the rod 54 and the plate 52. When the temperature surrounding the element reaches a point where the fusible material 51 melts, the 'rod54 and the core 39 will move downwardly due to the force of a compression spring 56 interposed between the core 39 and the top member 42 of the housing. A guide shaft 57 for the spring 56 extends axially upwardly from the core inside the spring 56. The downward movement of the core 39 is limited by an annular shoulder 58 onthe rod 54 which is adapted to engage the plate 52 when the-core '39 is substantially within the coil 38. After a fire has melted the fusible material 51 allowing the core 39 to move to its lower position,'the core may be returned to its upper position by holding'a hot iron or similar heating instrument adjacent the fusible material 51 to melt the material and allow it to flow around the rod 54 while'the core-is'held in its upper position. The iron is then removed and the coreheld in its upper position'until the fusible material solidifies to form a releasable connection between the plate 52 and the rod 54.

The amount of inductance change occasioned by the movement of the core 39 into the coil-38 depends upon the material of which the core 39 is made and'other magnetic circuit factors which are Well known to those skilled in 'theart. The unit is designed s'o'that the change of inductanceis sumcient to assure reliable operation of the relay 13. Since the system basically operates on an increase of impedance the number of stations affected by the fire condition is immaterial. It can now beseen that the present inventionprovides a fire detecting system which may have a large number of stations wherein each fire detecting station comprises 7 an impedance device, the impedance of which'is changed uponthe'occurrence of a fire condition to vary the current following throughthe device without the making or breakin'g of any contacts. Alarm means or other indicating means responsive to the change of current is provided to indicate the existence of a fire condition-and a system fault indicator is provided which operates in response to the total-interruption of the current in the system. While the preferred circuit arrangementfor use with the present invention utilizes a direct current component and a varying or alternating current component, it is possible'to utilize the present invention without the useof the two components. 'For example, the fault indicator relay 12 could be an A.C. relay held in a picked up condition by an alternating current of low magnitude and the relay'13 designed to drop out at an alternatingcurrent valuewhich maintains the relay '12 energized. The impedance change caused by the fire condition could then be adjusted so that when a fire condition occurs the relay 13 will drop out but the relay 12 Will remain energized. It should be noted however that the utilization of both alternating and direct current components inthc control circuit is advantageous Where a large number "of stations are likely to be affected by the fire condition, since the total increase in impedance caused bytheactuation of alarge number of stations might cause the AC. relay for the faulti-ndicator to drop out in a system which only utilizes an alternating current. i

The system could also be so designed that theffire alarm'relay iii-is ne rrnally in a dropped out-condition due to the high impedance breach station and the irnfied ance lowered by the existence of a fire condition so that the relay 13 is picked up to cause the energization of the fire indicating apparatus. The use of this type of system is not as satisfactory as the use of the A.C.-D.C. system where a large number of fire detecting stations are utilized since the change of impedance at one station only constitutes a small part of the total impedance of the system and would require a sensitive relay 13.

- The present system has been designed for use as a fire detecting and indicating system. It may, however, be utilized to detect and indicate or control the presence of conditions other than fire conditions. For example, the system may be used to indicate or control the presence of dangerous or undesirably high pressures in process apparatus.

Fig. 4 illustrates a detecting station modified so as to be pressure responsive. The detecting station utilizes a variable inductance having a spring biased core as in the first described embodiment. The inductance and core are located within a housing 60 which is the same as the housing 37 of the embodiment of the present invention shown in Fig. 3. The rod 54 for holding movable core of the coil in its normal position has been modified to extend externally of the housing 60 and is indicated in the embodiment of Fig. 4 by the reference numeral 61. The rod 61 is provided with a notch 62 adapted to receive a lug 63 carried on the-end of an actuating rod 64. The actuating rod 64 is adapted to be moved by the bellows 65 located within a cylindrical housing 66 mounted adjacent the housing 60. When the bellows 65 expands the rod 64 is moved in a direction necessary to move the lug 63 out of the notch 62 to permit the spring biased core within the housing 60 to move so as to increase the impedance of the inductance therein. The expansion of the bellows is opposed by a spring 67 interposed between the top of the bellows and the top of the housing 66. The top of the housing is threadingly attached to the housing so that the spring tension opposing the expansion of bellows 65 may be adjusted. The pressure to be controlled is supplied to the bellows 65 by a supply line 68 connected to the bottom side of the bellows. It will be seen that by the use of a plurality of detecting stations of the type illustrated in Fig. 4 indications of dangerously high pressures could be obtained in a pressure system. It will be well understood by those skilled in the art that the operation of the relay 13 could cause the energization of a work circuit to perform a control function rather than merely to give an indication.

Although the novel condition control or fire detecting system and detecting element for use therewith has been illustrated and described herein to a detailed extent it will be understood, of course, that the invention is not to be regarded as being limited correspondingly in scope but includes all changes and modifications coming within the terms of the claims hereof.

Having thus described my invention, I claim:

1. A fire detecting and indicating system including an inductance comprising a single coil having a movable core, releasable means for holding said core against movement in a first position and for releasing it for movement to a second position including detecting means responsive to a predetermined magnitude of a selected condition indicative of a fire for securing the core in its first position, said detecting means operating to release said releasable means upon said condition having said predetermined magnitude, said core being biased to said second position and moving thereto upon its release for movement by said detecting means whereby said inductance functions as a second position inductance, said inductance having a first magnitude when said core is at said first position and a second magnitude when said core is at said second position, circuit means for establishing a varying electrical current fiow through the whole of said coil for all positions of said core, the magnitude of said varying current being dependent upon the magnitude of said inductance,

a relay connected in series with said inductance and responsive to the change in said varying current occasioned by the movement of said core from said first position to said second position to change the magnitude of said inductance, and indicating means responsive to the operation of said relay to indicate the existence of a fire condition.

2. A fire detecting and indicating system including an inductance comprising a single coil having a movable core, releasable means for preventing movement of said core and for holding said core in a first position and releasing it for movement to a second position including detecting means responsive to a predetermined magnitude of a selected condition indicative of a fire for securing the core in its first position, said detecting means releasing said core and said core being biased to move to said second position upon the occurrence of said condition having said predetermined magnitude whereby said inductance operates as a second position inductance, said inductance having a first magnitude when said core is at said first position and a second magnitude when said core is at said second position, means for establishing an electric current through the whole of said coil for all positions of said core, said current having altermating and direct current components, the magnitude of said alternating current component being dependent upon the magnitude of said inductance, first and second parallel connected relays connected in series with said inductance, said first relay being responsive to the change in said alternating current component occasioned by the movement of said core from said first position to said second position to change the magnitude of said inductance, said second relay being responsive to an interruption of said direct current component, indicating means responsive to the operation of said first relay to indicate the existence of a fire condition, and an indicating means responsive to the operation of said second relay to indicate the existence of an open in said system.

3. In a condition control system, a control circuit ineluding a reactance device for determining the magnitude of the control current in said control circuit, said reactance device having a contact-free member movable to continuously vary the reactance thereof with the whole of said reactance device being included in the control circuit for all positions of said member, said member being biased to a first position wherein said device has a reactance of a first magnitude, holding means for releasably securing said member against movement and for holding the member in a second position against the action of said bias in which second position the reactance of said device is of a second magnitude, the last-said means including condition responsive means operable to release said member for movement upon the occurrence of a predetermined condition, said member being actuated to said first position upon the release thereof whereby said reactance device operates as a two-position reactance device.

4. In a condition control system, a control circuit including an inductance coil for determining the magnitude of control current flowing in said control circuit, said inductance coil being included in said control circuit in its entirety for all operating conditions of the circuit and having a movable core biased to a first position with respect to said coil, and means for holding said core against movement and for holding said core in a second position against the bias including condition responsive means operable in response to a predetermined condition to release said core from said holding means and to permit movement thereof to its first-said position by the bias thereon whereby said inductance coil functions as a twoposition inductance device.

5. In a condition control system for performing an operation only in response to a selected condition hav ing at least a predetermined magnitude, a reactance devic'e including a contact-free member movable to vary the magnitude of the reactaneethereof, said member being-biased to a first lposition,'releasable meanstforepreventing movement of Lsaid member and for releasably holding said'member in a second position against the 'b1as tending to move said member to said first position-, -'on e -of sa'id'positions being a relatively high reactance position and the other being a relatively low reactance position, the last-said means including detecting means responsive totsaid condition having at least, saidpredeten mined magnitude to release .said memberfor movement to said first position, the bias on said memberactuating saidmember to said first position upon the release thereof by said releasable means whereby said device functions as a two-position reactance device, circuit means for establishing a varying electrical current flow through the whole of'said reactance for all positions of said member, the magnitude of said varying current being dependent upon the magnitude of. said reactance, said c rcuit means including a first relay connected in circuit with said reactance and responsive to the change in said current occasioned by the movement of said member from said second position to said first position, and a second relay having a high alternating current impedance and a low direct current impedance connected in parallel with said first relay andresponsive to a failure of current therethrough.

'6. In a condition control system for performing an operation only in response to a selected condition having at least a predetermined magnitude, an inductance coil having a core movable to determined the magnitude of the inductance thereof, said core being biased to a first position, releasable means for'holding said core in a second position against the bias tending to move said core to said first position and for preventing movement thereof until the occurrence of said condition having at least said predetermined magnitude, the last-said means in-. cluding detecting means responsive to said selected condition having at least said predetermined magnitude to release said core for movement to said first position and said coil being actuated to'said first position by the bias thereon when released for movement by said releasable and responsive to the change in said current occasioned by the movement of said core from said second position to said first position, and second relay in parallel with said first relay and responsive to a failure of the current flow through the second relay.

'7. In a control system for performing a control operation only upon the occurrence of a selected condition having at least a predetermined magnitude, a control circuitincluding an inductance coil having a movable core for controlling the current in said control circuit, said inductance coil being connected in its entirety into said control circuit for all positions of said core, condition responsive means operatively connected to said core for holding said core in a position substantially out of said coil and for preventing movement of said core and for releasing said core for movement upon occurrence of said selected condition having said predetermined magnitude, and spring means operatively connected to said core urging said core to a position substantially within said coil, saidspring means being adapted to move said core into said coil upon the release of said core by said condition responsive means, and means for limiting the movement of said core into said coil.

; 8. A fire detecting and'indicat-ing system comprising .an inductance coil having a movable core having aportion extending from oneiend thereof, a member adjacent said portion, fusible means on said member for holding ment upon'the occurrence of a predetermined temperature condition, spring means engaging theend of said core remot'efrom said portion for actuating said core from said first-mentioned position to a second position upon the'release thereof whereby said inductance coil operates as a two-position inductance device, the inductance of said coil having a first" magnitude when said core is at said first-mentioned position and a second magnitude when said core is at said second position, means for establishing a varying electrical current through the wholeof said inductance coil and all positions of said core, the magnitude of said current being dependent upon the magnitude of the inductance of said inductance coil, and a work circuit responsive to a change in said current to perform a first control function and to a failure of said current to perform a second control function.

9. In a fire-detecting and indicating system, a firedetecting station comprising a housing, an inductance coil in said housing, a core in said housing supported for axial movement into and out of said coil, said core including a portion extending from one end thereof, a member supported by said housing adjacent said portion, fusible material connecting said portion to said member andholding said core in a first position generally out of'said coil,

spring means biasing said core to a second position genterial whereby said coil operates as a two-position inductance device, and abutment means carried by said core for engaging said member upon movement into said coil to limit the inward movement of the core, said housing having an access opening adjacent the outer end of said portion for permitting the resetting of said core to said first position. 7

10. A fire-detecting and indicating system including a variable impedance having a contact-free member movable to vary the magnitude of said impedance, said memher being biased to a first position and being actuated thereto by the bias when free tomove, releasable holding means for securing said core against movement and for holding said core in a second position including detecting means responsive to a condition indicative of a fire and releasing said member for movement, said member being operated to said first position by the bias thereon when released by said releasable holding means whereby said impedance functions as a two-position impedance device, the magnitude of said impedance having a first value when the member is at said first position and a second value when said member is at said second position, circuit means for establishing a current through the whole of said impedance, and indicating means responsive to the change in current in said impedance to indicate the existence of a fire condition.

References Cited in the 'file of this patent UNITED STATES PATENTS 421,854 Bulen Feb. 18, 1890 1,131,202 Boyden Mar. 9, 1915 1,355,041 'Harlow Oct. 5, 1920 1,909,212 Muehter May 16, 1 933 2,015,984 Wood Oct. 1, 1935 2,016,978 Thomas Oct. 8, 1935 2,318,005 McGuinness May 4, 1943 2,417,097 Warshaw. Mar. 11, 1947 2,431,352 Theillavmas Nov. 25, 1947 2,457,403 lSarver Dec. 28, 1948 V FOREIGN PATENTS 408,439 Germany Mar. 4, 1923 

